Several genealogical numbering systems have been widely adopted for presenting family trees and pedigree charts in text format. Ascending numbering systems Ahnentafel Ahnentafel, also known as the Eytzinger Method, Sosa Method, and Sosa-Stradonitz Method, allows for the numbering of ancestors beginning with a descendant. This system allows one to derive an ancestor's number without compiling the complete list, and allows one to derive an ancestor's relationship based on their number. The number of a person's father is twice their own number, and the number of a person's mother is twice their own, plus one. For instance, if John Smith is 10, his father is 20, and his mother is 21. In order to readily have the generation stated for a certain person, the Ahnentafel numbering may be preceded by the generation. This method's usefulness becomes apparent when applied further back in the generations: e.g. 08-146, is a male preceding the subject by 7 (8-1) generations. This ancestor was the father of a woman (146/2=73) (in the genealogical line of the subject), who was the mother of a man (73/2=36.5), further down the line the father of a man (36/2=18), father of a woman (18/2=9), mother of a man (9/2=4.5), father of the subject's father (4/2=2). Hence, 08-146 is the subject's father's father's mother's father's father's mother's father. The atree or Binary Ahnentafel method is based on the same numbering of nodes, but first converts the numbers to binary notation and then converts each 0 to M (for Male) and each 1 to F (for Female). The first character of each code (shown as X in the table below) is M if the subject is male and F if the subject is female. For example 5 becomes 101 and then FMF (or MMF if the subject is male). An advantage of this system is easier understanding of the genealogical path. The first 15 codes in each system, identifying individuals in four generations, are as follows: Surname methods Genealogical writers sometimes choose to present ancestral lines by carrying back individuals with their spouses or single families generation by generation. The siblings of the individual or individuals studied may or may not be named for each family. This method is most popular in simplified single surname studies, however, allied surnames of major family branches may be carried back as well. In general, numbers are assigned only to the primary individual studied in each